Signaling



' Aug., 2E, E923.

R. A. HElSlNG Aug. 2H, H923. l

` R. A. HEISING SIGNALING Filed sept. 29, 1919 3 sheets-sheet 2 V450, 000 0f rm500, 000

/T jv-n" 7000 l /7 ^u= 500,000 rc y 2? 25 C o f |9: 550.00%@

Patented Aug. 2i, 1923.

einer casina.

RAYMOND A. HEISING, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN' ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A. CORPORATION OIE' NEW YORK.

SIGNALING.

To aZZwhom t may concern.'

Be it known that I, RAYMOND A. HEisiNc, a citizen of the United States, residing at East Orange, in the county of Essex, State 5 of New Jersey, have invented certain new and useful Improvements in Signaling, of which the following is a full, clear, concise, and exact description.

This invention relates to transmission systems andA more particularly to high fre` quency signaling transmission systems.

The general object of the invention is to provide more eiiicient and` selective and therefore improved means for and methods of transmission by high frequency waves. The means and methods outlined are more particularly adapted vfor wireless telephony, but the principles of the invention are also applicable to telegraphy and telephony either with or without wires.

A particular object is the provision of improved means for multiplex or other communication systems whereby interference due ,to certain parasitic and undesirable waves of certain frequencies is eliminated.

A further object is the provision of means whereby electromagnetic waves of certain components are transmitted, which waves produce at a receiver the useful effects which would be producedby a plurally modulated wave without causing interference with other. signaling systems to the same extent as is often true in the-case of the transmis sion of plurally modulatedl waves.

. The invention has for a further object to produce a wave having certain characteristics of a plurally or successively modulated wave without performing the operation of plural or successive modulation. y

Further objects will be apparent totliose skilled in the art from a perusal of thefollowing detailed description. i

In the accompanying drawings, Fig. 1 illustrates diagrammatically the wave lengths transmitted by a pluralor a successive modulation system where theharmonics of the intermediate frequency are present; Figs'Q- to 5 inclusive represent transmission systems involving the principles of the invention Fig. 6 is a simple form of receiving systemy adapted to receive messages from such systems as shown in Figs. 2, 3 and 4; Fig. 7 is a 4form of receiving system adapted for receiving a plurality of messages suchl as can be transmitted by means ioI modulated wave, that is, a wave of carrier frequency p which has been modulated'iii accordance with a supplemental carrier wave of frequency c7, the supplemental wave of frequency g being already mqdulated in accordance with a signaling wave of frequency s where s represents, in the case of telephony, thefrequencies necessary for the reproduction of speech. As shown in Fi 1 waves would be transmitted having the reqencies p, pel-g, and p-g, also the bands of frequencies p14-gis and p-gi-s. Since, however,

there will always be present a greater or less portionv of harmonics of the frequency gA which may be designated g1, g2, etc., additional frequencies and bands of frequencies will be transmitted as shown in Fig. vl. This necessarily results in confusion between stations and between the various messages of` one and the same station where multiplexing iscarried out by using a plurality of supplemental carriers g each having a different frequency and each being modulated in accordance with one or morel signals. By means of the systems herein described the harmonics of the supplemental carrier wave of frequency g will be eliminated and any other harmonics introduced will be far out of the working range of the frequencies being transmitted. Fur-A thermore, the side band which includes one of the sets of frequencies p-g and {1i-gis or pel-q and p-l-gi-s may be/eliminated if desired. v

In Fig. 2 a wireless transmission system is shown which is adapted to producevand radiate a wave of frequency 172500,000 and a modulated wave of frequency o4-gis: 550,0001-8. The oscillator O comprises any suitable means and is herein represented as a thermionic vacuum tube suitably connected to afcircuit arrangement to 'generate oscillations of the frequency of 500,000 cycles per second. These 'oscillations are impressed upon the input circuit 1 of an amplifier syswith practical forms of. generators Y v be modulated in accordance with signa-ls.

In the present instance this is accomplished by placing the anode-cathode circuit of the vacuum tube 3 of the oscillator O' in shunt to the anode-cathode circuit of vacuum tube 4, Whose impedance is varied in accordance with waves of signaling frequency in the microphone circuit 5. A common source 6 supplies space current to tubes 3 and 4 through the speech frequency choke coil 7 The amplifying system A impresses upon v the antenna system 7 the waves impressed upon its input circuit by the oscillators' O and O'. The system 7 typites any suitable type of radiating or other transmitting circuit.

Referring to Fig. 3 the oscillator O functions in a manner similar to the corresponding oscillator in Fig. 2. In addition to the oscillator O another oscillation generating system O is provided. The set of vacuum tubes 4, to whose input circuit is connected the source 5 of the signals to be transmitted, is connected to each of the oscillation generators 0 and O so that the oscillations of each may be modulated in accordance with the same signal. The means provided for accomplishing this result consists of the common source 6 and a choke coil 7 functioning as in the arrangement of Fig. 2. Keys 8, 9 and 10 are provided. When the key 8 is opened the oscillator 0 ceases to impress oscillations upon the input circuit 1 andi' when the keys 9 or 10 respectively are opened the generators O' and O cease to generate oscillations. The amplifying system A and i the transmission line 7 function to transmit whatever waves are being generated by the oscillators O and O".

In Fig. 4 thesources 11 and 12 produce unmodulated oscillations having frequencies of 550,000 and 450,000 cycles per second respectively. The source 12, however, may be adjusted to generate oscillations having a frequency of 500,000 cycles per second for thereason hereinafter mentioned. The oscillations so produced by the sources 11 and 12 are impressed upon the input circuit 13 of a thermionic amplifier 14 whose anodecathode path is in arallel with the anodecathode path of a t ermionic device 15 with respect to source 16 and the speech frequency choke coil 18. To the input circuit 19'of the device 15 is connected any suitable source y 20 such as a microphone circuit or telephone line. 'Ifhe impedance of the device 15 will be varied 1n accordance with signaling waves in the circuit 20 which will cause a correspondaccordance with a signal individual thereto.` All the waves generated are impressed upon the input circuit of the amplifier system A and radiated by the transmission circuit 7.

The circuit illustrated in Fig. 6 is adapted i to receive Waves sent out from transmitting systems such as shown in Figs. 1, 2, 3 and 4. The system is also adapted to selectively receive one of the high frequency signaling waves transmitted 4by the system in Fig. 5. The receiving system comprises a suitable receiving conductor 21 coupled to a tuned circuit 22 which will in general be tuned to the mean frequency of the waves to be received. The circuit 22 is in the input circuit of a detector 23 whose output circuit includes a tuned circuit C to which is connected a similar circuit D, which in turn is included in the input circuit 24 of a second detector 25 whose output circuit comprises a telephone receiver or other suitable indicating instrument 26.

In receiving waves from a system such as shown in Fig. 2 the wave having a frequency of 500,000 cycles per second and the modulated wave of 550,000 cycles per second are,

impressed upon detector 23, thereby producing in the circuit C a wave having as one component a frequency of- 50,000 cycles. The 50,000 cycle wave corresponds to the intermediateor auxiliary carrier wave in a plurally modulation system. Thus it -is seen that althouo'h this auxiliary wave is not generated at the transmitter the same effect is produced at the receiver as if it were bein generated at the transmitter. The circuits and D re resent any suitable selective circuits to .reproduced in the device 2 lter interfering waves from the' auxiliary carrler Wave. This wave will. be",

The arrangement illustrated in Fig. 3 may A 'l be used to transmit in several different. ways.

If one only of the oscillators O' and O" is operating and the oscillator O- is idle, then the wave transmitted will be an ordinary modulated wave and may be received by a s stem comprising 'a single detector.' .If both t e oscillators 0' and O are operating, a

iso

Lacasse system such as Fig. 6 may be used to receive the resulting signaling wave either by tuning the circuits C and D to select a wave having a frequency of 100,000 cycles or by applying from a local source 27 to the input circuit of detector 23 a wave having a frequency of 500,000 cycles. In this case the circuits C and D would be tuned to select a wave Aof 50,000 cycles. This4 signal could, however, be detected by a single detector having selective circuits for receiving a wave of 450,- 000 'cycles or 550,000 cycles. If the generator O is operating and either or bothof the generators O' and O are operating, then the arrangement of Fig. 6 may be used to receive by tuning the circuits C and D to select an auxiliary carrier frequency Wave of 50,000'cycles.

The receiving system illustrated in Fig. 7 is similar to that shown in Fig. 6 except that additional sets of tuned circuits C', D', C, D", etc., are provided. These circuits will be arranged to select auxiliary carrier frequency waves of 50,000, 40,000, 30,000, 20,-

' 000 and 10,000 cycles respectively corresponding to those waves which will be produced by radiating waves of 550,000, I540,000 cycles, etc., together with 500,000 from a system such as shown in Fig. 5 and detecting them bymeans of a detector 23. The auxiliary carrier frequency waves are seen to have frequencies higher than the frequencies essential to the accurate reproduction of articulate speech. The auxiliary local source 27 is not shown in Fig. 7 since lit is entirely unnecessary for selective reception of the several signals so long as a wave having a frequency of 500,000 cycles is being received from a system such as shown in Fig. 5 or from some other system.

Fig. 8 illustrates a group of transmitting stations 28, 29, 30, 31 and 32 each arranged to transmit a different modulated signal wave gis, gli-8 etc. yThev frequency g may be 550,000 cycles, g', 540,000, etc. Stations 33, 34, 35, 36 and 37 represent a group of receiving stations at each of which it is desired to receive one of the signals sent out from the transmitting stations without interference by any of the others. This is accomplished by sending fromstations 28 or from any other suitable source a Wave p having a frequency of 500,000 cycles. If the stations 33, 34, etc., are like that illustrated in Fig. 7, each station will beenabled to selectively receive the message lrheilig transmitted from any of the stations 28,29,etc. Furthermore, it will be possible for 'each station '33, 34, etc., to simultaneously receive, if desired, the messages being sent out from stations 28, 29, etc. It is unnecessary to have a local source at any of the receiving stations and it is necessary to have only one source of waves of frequency p at one of the transmitting stations. This source may, if desired, be at some other station which is not engaged in transmission. kThe interfering waves which would be due to modulation of the carrier wave of frequency p by harmonics of waves of the auxiliary frequencies g, q1, etc., are eliminated. Furthermore it will be seen by reference to Fig. 1 that where a plural modulation system of the ordinary type transmits waves both above and below any carrier frequency p, the system herein described will produce equally eliicient waves. thereby leaving free the remainder of the wave lengths for the transmission of other messages between other signaling stations.

The novel features believed to be inherent claims. i What is claimed is:

1. The method of multiplex signaling which comprises transmitting a plurality of carrier waves, each modulated in accordance with speech, which carrier waves have frequencies diering `too slightly to be etliciently selected at a receiving system and transmitting along with said waves a wave of a frequency differing from any thereof andy combining said Wave with each of said ca rrier waves in order to produce at a receivingsystem speech modulated waves of such characteristics as to be readily separated.

2. The method` of separately receiving a plurality of radiated Waves, all but one of which are modulated in accordance with a signal wave, which comprises producing at a receiverthe difference frequencies between each of said modulated waves and said one Wave, selecting the difference frequencies, and separately detecting the selected waves to produce the signal wave according to which the corresponding modulated wave is modulated.

3. The method of multiplex signaling which comprises transmitting a plurality of waves each modulated by a signal wave and simultaneously transmitting a base frequency wave, causing said modulated waves tointeract at a receiver with said base frequency wave to produce auxiliary frequency waves of frequencies above the highest range ofv frequencies necessary for the production of audible speech, and in separately detecting the auxiliary frequency Waves.

4. The method of telephone communication between two widely separated stations to be separted at a cooperating receiving station. Y L

6. A transmission system. comprising means for. producing, .modulating in accordl'ance vwith individual sound signals and transmitting each of a plurality of waves,A

and means for producingand transmitting therewith a wave of afrequency'enabling each one of vsaid waves to be separated from the others at a receiving station to rel produce the vmodulating sound.

ceiving means ada ted to' receive said waves and produce there rom waves of frequencies P9i27qv 29.4.92, etc., at least one of said produced waves being of superaudible fre quency, and means for deriving and separ ately indicating .the individual signals from each of said last mentioned waves.

8. A system comprising a plurality of transmitting stations and a plurality of re-V ceiving stations, means for transmitting a carrier wave modulated in accordance with a signal wave from each of said transmitting stations, means for transmitting from a single source an unmodulated wave, and means at each of said receiving stations for combining energy derived from said unmodulated wave with energy derived from said modulated waves in order to selectively receive the signal carried by one of said modulated waves.

9. A multiplex communication system comprising means for transmitting through the same medium a series of carrier waves differing in frequency by a slight percentage of the frequency of the lowest thereof, means for transmitting another-wave, means at a rece1v1ng station for combining said serles.

of waves with energy of said other wave and producing a corresponding series of carrier waves whose frequencies differ by a relatively great percentage of the frequency of the lowest thereof, electrical selecting means for selecting such of said last mentioned waves as are desired to be received at said receiving station, and means, for deriving signals therefrom.

10. A carrier wave transmitting system comprising'means for transmitting anunmodulated wave and means for transmitting therewith either a signal modulated wave having a carrier frequency greater than said iirst mentioned wave by a given amount or a wave having a carrier frequency less than said first mentioned wave by said given amount, said means being capable, of changing the modulated wave from one frequency tothe -other without interruption of signaling or the'transmission waves other than the frequencies energy of the modulated and unmodulated waves to a transmitting conductor for transmission to a distant point, and" channels fortransferring said modulated and unmodulated waves to said common means, said channels each including elements rendering them selective of one of said waves to the exclusion of other waves. 12. A system inacordance with claim 11 in which the common means comprises an amplifier for increasing the energy of the waves before transmission. 13. A` system for signaling comprising two sources of high frequency waves differing by a frequency above good audibility, means forv modulating the waves from both of said sources in accordance with the same signal wave to produce modulated waves, a common means for transferring the energy of the modulated waves to a transmitting conductor for transmission, and channels for y transferring said modulated waves to said common means, said channels including elements rendering them selective of one of said waves to the exclusion of other waves.

14. A system in accordance with claim 13 in which the common means comprises an amplifier forincreasing the energy of the waves before transmisslon.

15. A system for signaling comprising a plurality vof sources of high frequency waves diifering by a frequency of at least 2,000 cycles per second, means for modulating the waves from each .of saidsources in accordance withindividual signal waves of audible frequencies to produce modulated waves'ofthe same carrier frequency as the unmodulated waves, a common means for increasing the energy of the modulated waves before impressing them upon a trans-v 17. Ina signaling system for vtransmitting two waves of different frequencies modulated in accordance with the samesig# nal, arrangements for providin wave'l energy fof the twoifrequenc1eslan a constant current modulating system for varying the amplitudes of the two Waves in accordance with the signal, in combination with means for transmitting the energy of the modulated Waves.

18. A signaling system for producing and transmitting from a single station a plurality of carrier waves of different frequencies, means for'modulatin said carrier Waves, means for transmitting fromA amount above audibility but less than will convertin enable their direct separation by selective apparatus which comprises transmitting from a station remote from the placesof reception and transmission energy of a definite wave frequency, combining at the place where any one of the effects is to -be received energyl of the definite Wave frequency with t e energy corresponding to the effect to be received, segregating a resultant energy inherently containing the effect to be produced from other resultant energies inherentl containing undesired effects, and producmg the desired effect from the selected energy.

20. The method of transmission which comprises generating and transmitting a signal modulated carrier Wave and generating and transmittin a Wave differing therefrom in frequency y an amount above the range of frequencies used for the reproduction of audible speech, receiving said modulated and unmodulated Waves at a receiving station and combining them to produce a combination frequency Wave, separating the combination frequency wave from other waves by electrically selective means, and the selected Wave to reproduce the signa 21. The method of transmission and reception which comprises generating and modifying a high frequency wave, transmitting said `Wave to a distant point, generating and transmitting with said wave another wave differing therefrom in frequency by an amount greater than 2,000

cycles per second, receiving both of said waves at a receiving station and combining their energies to produce a combination frequency Wave, electrically selecting said combination frequency Wave to separate it from other Waves, and distorting said selected Wave to produce indications corresponding to the -modification of the modied wave transmitted.

22. A system of communication comprising a transmittin station vhaving. lmeans for generating an transmitting two waves of dierent frequencies, and a receiving system for receivingsaid waves, said rece1ving system comprising a device for combining said waves to produce aA combination frequency wave, means for selecting said combination frequency Wave, and distorting means for converting the frequency of said combination frequency Wave.

23. A. system ofV transmission comprising a transmitting station having means for generating and transmitting two waves of different frequencies together with means for modifying both of said waves by indications to be transmitted, and a receiving system, said receiving system comprising a device for combining said Waves to produce a combination frequency Wave, means for selecting said combination frequency Wave from other Waves, and distorting means for converting said combination frequency Wave to produce the indications.

24. In a system for selective transmission and reception, apparatus for producing, and a channel for transmitting, a high frequecy wave modified in accordance with indications to be reproduced at a receiver, means for producing another wave, means comprising a channel-other than the channel for transmitting the modified Wavefor transmitting in unmodified form energy of the second Wave, a receiving station adapted to receive and combine the energy of the modified and unmodified Waves to produce Waves having a frequency above the usual range of frequencies ofv audible sounds, and means for utilizing said produced Waves to reproduce indications corresponding to the modifications of the modified trans-l mitted wave.

In'witness whereof, I hereunto subscribe my name this 27th day of September A. D., 1919.

RAYMOND A. HEISING. 

